13A / USB socket power drain?

[dennis]

It makes quite a nice bang if it has PoE on that socket and they don't have proper current limiting.

[Richard Conway]

Don't think I've ever come across a PoE switch that provides power without first negotiating how much.

[charles]

You can also get "nice bang" from Figure of 8 mains connector pushed into an XLR 3 pin audio plug.

[dennis]

How does it negotiate without powering the attached device?

[Richard Conway]

I realised that after I'd hit send. D'oh!

[Tim Watts]

There were some crappy "PoE" supplies that followed no particular standard and just shoved power over a pair of pairs.

[Tim Watts]

I'm going to guess that it supplies minimum power to allow the client PoE chip to power up (without the rest of the device) and that does the negotiation. Think of a TV on standby and the remote still works.

[tabbypurr]

You can also harvest power from data - which it actually does I don't know.

[John Rumm]

You might want to think through the implications of that on a CSMA-CD network...

[Andy Burns]

Ethernet using* CSMA/CD is essentially non-existent today.

[*] 10/100Base-T cards are still capable of it in case they find themselves plugged into a hub, rather than switch.

[Tim Streater]

:-)

Reminds me of the physicists where I used to work who though it was OK to extend the thinnet segment with 50 metres or so of their very thin

50 ohm signal cable.

Hey, it's 50 ohms, innit?

[Andrew Gabriel]

Get loads of broken microUSB sockets at repair events. The leverage you can generate with the plug, combined with a surface mounted socket, is just a recipe for disaster. With heavier items such as tablets, dropping them with the microUSB plugged in is also a cause of breakage.

Sockets also wear - eventually one of the metal leaves comes away from the centre support.

[The Natural Philosopher]

And to a degree, it works too.

[Hanny Z]

But you never see the much higher number of broken plugs at repair events, because they are so easy and cheap to replace, as they were designed to be.

Sure, no design can ever be perfect in that area and still be affordable to produce and be viable in very small devices like phones.

But long after the plug has been replaced very cheaply multiple times.

I prefer the Apple lightning connector myself, but it has the other approach, you are more likely to see the socket that is much harder and more expensive to replace be what needs to be replaced. And easier to damage it by using cheap chinese cables that have the plug too thick too.

[Tim Watts]

I have never replaced a plug - has anyone?

The Apple maglock plug was probably the best in terms of being bomb proof for power at least.

[Andrew Gabriel]

I've had a couple of USB thumb drives with the type A plug at repair events, with the plug snapped off due to dropping laptop with it plugged in. One drive held the only copy of someone's thesis, and we managed to solder it back together well enough to read the data off. Some similar storey for the other one too.

Yes. Apple are extremely protective of the associated patents.

[Bob Eager]

Unless they are someone else's.

[Dave Liquorice]

"easy and cheap to replace" you mean bin the lead, buy a new one. I've yet to find a source of wireable microUSB plugs, indeed finding any wireable USB plug is pretty much impossible.

[Hanny Z]

Yes, that's the way the micro USB system was designed.

Because it makes a lot more sense to buy a chinese made lead for 50p.

[Dave Liquorice]

802.3af or 802.3at won't. "Passive" does and those cheap stepping LED network testers don't like 12 V passive "PoE" either... 802.3at or .af PSE detects the precense of a PD on a cable by looking for signature resistance of 19 to 26.5 K ohms across the powered pairs, to do this it uses a voltage pulse between 2.7 and 10.1 V. If the PSE finds this signature resistance it uses a slightly higher voltage pulse to determine the PD power class before finally applying

powered the PD must draw 5 - 10 mA for at least 60 ms and no more than 400 ms between these draws. ie half a second after a PD is unplugged or switch off (if it has a switch!) the power is removed.